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Wednesday, May 4, 2016

Fundamental (trans-Planckian) large spins are expected to decay intomany small spins under the dynamics. An explicit calculation showing this has been given now within group field theory. At the same time,one can coarse grain the many small spins into few large spins to havean effective continuum description. The precise relation between thosetwo, a priori distinct large spin regimes is so far unclear.

The fundamentally important issue of low and high spins in the dynamics of LQG has been discussed in previousposts. In short, large geometries can be described using either many low or few large quantum numbers (SU(2) spins), but the respective dynamics needs to be interpreted with care. In particular, using large spins to describe continuum geometries requires to understand the renormalisation group flow of the theory. Most work in LQG has so far been in the context of large spins (without considering renormalisation), where calculations simplify drastically due to the availability certain asymptotic formulae for the SU(2) recouping coefficients with nice geometric interpretations. However, there seems to be some progress now on the low spin front.